One of the structures of the human eye is the eyelid. A medical condition that may afflict eyelids is cancer, as more than one type of cancer may afflict eyelids, the cancers are generally referred to as eyelid cancers.
Human eyelids consist of an upper eyelid and a lower eyelid. The upper and lower eyelids cooperate to conceal or expose a portion of an underlying eyeball. In performing this function, the lower eyelid has relatively little movement, while the upper eyelid acts much like a shade. The shade action is facilitated by what is commonly known as a “crease,” which permits some of the eyelid to overlap itself when the eyeball is exposed. The crease varies depending upon ethnic background. For example, the upper eyelids of people with an Asian background tend not to have a pronounced “crease,” which is found in people with a Western background.
An eyelid has two opposing surfaces—a visible external surface, i.e., skin, and a non-visible interior surface, i.e., a tarsal plate, which “rides” on the eyeball. Between these two opposing surfaces, or structures, within the eyelid are various other structures, such as muscle and fat. The eyelids also have eyelashes. It is possible with either eyelid to pull the eyelid away from the underlying eyeball to create a gap.
Eyelid cancer is a general term for any cancer that occurs on, or within, the eyelids, upper or lower. Malignant eye cancers include basal cell carcinoma, sebaceous carcinoma, squamous cell carcinoma, and melanoma.
Eyelid cancers occur in multiple structures of the eyelids. More specifically, basal cell carcinoma is found under the squamous cells in the lower epidermis, which is the outer layer of the skin. Sebaceous carcinoma is found in the meibomian glands and the glands of Zeis. Squamous cell carcinoma is found in the squamous cells, which are located in the lower epidermis. Melanomas are found in the deepest layers of the epidermis.
Eyelid cancers are staged (or quantified) by the TNM system. Under the TNM system, a cancer can be staged as a TX, T0, Tis, T1, T2, T3, or T4 cancer. Associated with the T1, T2, and T3 designations are size limitations. A T1 stage cancer has a cancer growth of 5 mm or smaller in diameter, or is not invading the tarsal plate. A T2 stage cancer is between 5 mm and 10 mm, or has invaded the tarsal plate. A T3 stage cancer is greater than 10 mm, or has spread into the full thickness of the eyelid.
Treatment options for eyelid cancers are based on the type of cancer and the stage. Treatment options include surgical removal, such as surgical biopsy (e.g., incisional or excisional), Mohs' surgery, or cryosurgery. Non-surgical options include using high-energy x-rays from a machine outside the body to bombard the cancer. A radiation/surgical option is brachytherapy (i.e., surgical implantation of radioactive material in the cancer).
Each procedure has its own side effects. Surgical procedures may result in infection, pain, and the need for plastic surgery, such as for reconstruction or for changes in eyelid position. Side effects of radiation treatments not only include infection, pain and potentially the need for plastic surgery, but also rashes, dry skin, skin color change, cataract development, loss of eyelashes and/or dry eye, red eye, tearing, sensitivity to light, retinopathy, optic neuropathy, and neovascular glaucoma. Some complications from radiation treatments can lead to the need to remove the eye.
Despite the potential complications, radiation treatment of eyelid cancers is an efficacious treatment that offers the potential to avoid plastic surgery, which is common with a surgical procedure. Therefore, where an eyelid cancer is susceptible to radiation treatment, a radiation treatment would be preferred if the undesirable side effects could be reduced or eliminated. As a result, what is needed in the art is a better method of delivering radiation to an eyelid cancer so that damage to other organs, such as the eye, is at least minimized.